The present invention relates to the field of particle beam analysis equipment.
It is frequent to want to characterise a particle beam in various applications such as in the fields of fundamental physics, biophysics, machines for the producing synchrotron radiation, and more generally any charged particle beam.
Prior art already knows analysis equipment that makes it possible to detect and characterise a particle beam, such as wire chambers. Such devices require a gas supply involving a supply and regulation device but also a safety system and monitoring by a qualified operator. They are cumbersome, not flexible, difficult to use, to handle and to maintain.
U.S. Pat. No. 4,942,302 is also known describing a device comprising two detectors each coupled to a plane of scintillating fibres respectively extending in a horizontal direction for one and in a vertical direction for the other. Said detectors comprising scintillating optical fibres having a reading system based on photomultiplier tubes (PMT) which obtain a signal which is then amplified then converted into a digital signal.
The present invention more specifically relates to equipment for analysing a particle beam comprising:
at least one detector comprising a network of optical fibres (9), the network of fibres comprising at least one first plane of optical fibres oriented according to a first direction X;
the detector being arranged to produce a light signal when the particle beam passes through the network of optical fibres,
an image sensor coupled with the detector such as to output a signal representing features of the light signal.
Such equipment is known from the French patent application FR 2 849 697. In said patent application, the image sensor comprises a photomultiplier tube. It is well known that such a photomultiplier tube can produce a detector of a light beam only particle by particle. In the equipment described in the abovementioned French application, a dosage of the particle beam is thus produced counting one by one the particles of said beam. Due to said particle by particle counting, the Applicant has demonstrated that such equipment equipped with a photomultiplier tube can only detect less than one million (106) particles per second. To obtain a better detection rate, the current induced in the photomultiplier tube becomes too substantial and extremely complex electronics would be required at the outlet of the photomultiplier tube. For a detection rate greater than one million particles per second, such equipment comprising a photomultiplier tube is therefore very limited by the intensity of the particle beam. For many years, the person skilled in the art has attempted, from such equipment with a photomultiplier tube, to provide an electronics that can process such particle beam intensities.
Furthermore, the photomultiplier tubes have the disadvantage of not being able to be used in the vacuum, where preferably the beams circulate. Furthermore, only a dosage of the particle beam is directly possible with such equipment. In particular, it is not possible, with such equipment, to directly measure the average position and/or intensity and/or the spatial and temporal dispersion of a particle beam.
The invention notably aims to overcome said disadvantages. One aim of the invention is to provide equipment for analysing a particle beam such as above described, which can be effective in a wide range of particle beam intensities, for example between one thousand (103) and ten thousand billion (1013) particles per second. The invention also aims to propose equipment having an easy implementation, suitable for an industrial type structure. The invention also aims to provide equipment which is highly stable over time, requiring no maintenance, and having no saturation phenomenon. The present invention also aims to provide analysis equipment which enables the average position and/or the intensity and/or the spatial and temporal dispersion of a particle beam to be measured.
At least one of said problems is solved by the invention, which relates, as abovementioned, to an equipment for analysing a particle beam comprising:
at least one detector comprising a network of optical fibres (9), the network of parallel fibres comprising at least one first plane of optical fibres oriented according to a first direction X
the detector being arranged to produce a light signal when the particle beam passes through the network of optical fibres,
an image sensor coupled with the detector such as to output a signal representing features of the light signal,
wherein the image sensor comprises a CCD or CMOS sensor, and wherein the ends of the optical fibres of the network of fibres are arranged to form an image of the light signal in the object plane of the CCD or CMOS sensor.
With the aid of the CCD or CMOS sensor, the Applicant has notably demonstrated that much higher particle beam intensities could be analysed satisfactorily. Thus, instead of looking to develop electronics adapted to high intensities, the Applicant has modified the most widespread image sensor of the prior art. Surprisingly, she has demonstrated that the use of CCD or CMOS sensors enabled the abovementioned disadvantages to be overcome.
Furthermore, the CCD or CMOS sensors have the advantage of being useable in cameras comprising processing means suitable for processing the information acquired by the CCD or CMOS sensor for a high particle intensity. The CCD or CMOS sensors also have the advantage of being useable in the vacuum. With the aid of the levels of particle beam intensities obtained according to the invention, the Applicant has demonstrated that it was possible to use the invention for hadrontherapy.
According to the invention, the preferred sensor is a CCD sensor because it enables particle beams to be measured for very high intensities. The CMOS sensor also enables the problems linked to the intensity to be solved, but in an intensity range slightly lower than that of the CCD sensor. According to one embodiment of the invention, the network of fibres can comprise a first plane of parallel optical fibres oriented according to a first direction X and a second plane of parallel optical fibres oriented according to a second direction Y, the ends of the optical fibres of each plane being arranged to form the image of the light signal in the object plane of the CCD or CMOS sensor.
According to one embodiment of the invention, the ends of the optical fibres of the network of optical fibres are brought together at the outlet of the detector to form the image of the light signal in the object plane of the CCD or CMOS sensor. This has the advantage of limiting the size of an objective which can be placed between the ends of the fibres and the object plane of the CCD or CMOS sensor. According to one embodiment, the beam of fibres of the first plane is substantially co-planar with the beam of fibres of the second plane, the end of said two beams of fibres forming two contiguous images. The CCD or CMOS sensor is chosen to be able to receive said two contiguous images, which can be juxtaposed or straddled on the sensor.
According to one embodiment, the ends of the beams of fibres of the first and second plane are brought together in the same object image plane. According to one particular implementation, the equipment comprises an ultra-high vacuum flange, and the object image plane is formed behind the ultra-high vacuum flange. Advantageously, said CCD is directly mounted in the object image plane.
According to one variant, said CCD sensor is built into a CCD camera. According to one mode of implementation, the detector comprises two stages linked by an ultra-high vacuum flange. According to one embodiment, the ultra-high vacuum flange is equipped with a port for passage of the light emitted by the fibres.
According to one embodiment, the first stage comprises two identical armatures wherein the optical fibres are urged to be placed. Advantageously, each of the armatures of the first stage respectively corresponds to the horizontal and vertical coordinates of the particle beam by fixing at 90° the angle between the two planes of fibres. According to one variant, the first stage is located in the vacuum tube of the beam. According to another variant, the second stage comprises an optical system associated to a CCD digital camera.
Advantageously, the scintillating optical fibres are aluminised over their entire length. According to one implementation, the optical fibres are manufactured in polystyrene. According to another embodiment, the second stage benefits from an electromagnetic shielding. According to one variant, the images are transferred on a PC type computer. Advantageously, the CCD sensor is formed by CCD arrays with an associated digital electronics. The invention also concerns the use of the abovementioned analysis equipment for hadrontherapy.